1. Field of the Invention
The present invention relates to a medical needle assembly, and a medical device incorporating the same in the tubing line between a needle inserted into the blood donor's vein and a blood bag, and so comprised as to permit the collection of a blood sample for testing following the collection of blood in the blood bag.
2. Description of the Prior Art
Samples of blood collected from a donor in a blood bag are collected with evacuated sampling tubes and other devices for a variety of determinations. As with blood collection in a blood bag, this must be done under contamination-free conditions. Many medical needle assemblies, and medical devices incorporating the same in the tubing line connecting the blood bag and the venipuncture needle, have been developed for this reason. Typical of these are U.S. Pat. Nos. 3,127,892, 3,217,710, and 3,342,179. In U.S. Pat. No. 3,127,892, the junction consists of two rubber sleeves that couple with each other by means of a protruding ring and a matching groove that interengage; the two sleeves separate when pulled apart by hand. This type of arrangement has a number of disadvantages. First, because the rubber sleeves are joined by the interengagement of a ring and a groove, the tensile strength is less than about 500 grams, resulting in a weak coupling force. This means that during production or use, the sleeves may separate, presenting a risk of fluid leakage or bacterial contamination. Moreover, as the two sleeves are merely interengaged, it is difficult to check whether the sleeves have been disengaged and separated prior to use. Hence, this type of arrangement is not adequately tamper-proof.
In U.S. Pat. Nos. 3,217,710 and 3,342,179, the hub assembly incorporating the needle consists of two integrally formed sections provided therebetween with a "weak" or "breaking" point. At the required time, the two sections are twisted apart and used. This arrangement makes it easy to check whether the device has been opened prior to use, and is therefore tamper-proof. However, because the breaking strength of the thin-walled weak point formed between the two sections is not uniform, and is at times too large, wings have been added to aid in twisting the two sections apart.
Although integral formation of the hub and protector appears to be a reasonable approach, this in fact presents a host of problems. To begin with, the formation of a long, thin-walled composite hub and protector requires a high level of technical sophistication. Accordingly, it is difficult to form a small, thin-walled weak point. The inevitable result is a tendency to make the point that should be thin-walled relatively thick instead. This means that a greater force is required to twist-snap the two sections apart, which tends to decrease product uniformity. In addition, precise production molds must be used, raising costs.